The present invention relates to an grounding construction of a multilayer printed circuit board.
FIG. 1 is a cross-section of a typical example of conventional earthing constructions of multilayer printed circuit boards. In FIG. 1, a reference numeral 1 designates a first printed circuit board, 2 a second printing circuit board, 3 and 4 conduction patterns oppositely provided on the outer surfaces of the first and second printed circuit boards 1 and 2, respectively 5, 6, 7 and 8 through holes provided in the conduction pattern 3, first circuit board 1, second circuit board 2 and the conduction pattern 4 respectively for passing an electric part therethrough. The electric part 9 is inserted in the through holes 5, 6, 7 and 8 so that its both ends protrude from the outer surfaces of the first and second circuit boards 1 and 2 slightly and the protruded both ends are fixedly soldered by solders 10 and 11, respectively. A reference numeral 12 designates an grounding conduction pattern provided on the outer surface of the first printed circuit board 1, 13 an grounding conduction pattern provided on the outer surface of the second printed circuit board 2 in opposition to the grounding conduction pattern 12, 14, 15, 16 and 17 through holes provided in the grounding conduction pattern 12, first printed circuit board 1, second printing circuit board 2 and grounding conduction pattern 13 for passing a pin A therethrough. The pin A is inserted in the through holes 14, 15, 16 and 17 so that both ends thereof protrude from the outer surfaces of the first and second circuit boards 1 and 2 slightly and the protruded both ends are fixedly soldered by solders 18 and 19. One end of the grounding conduction pattern 13 is fixedly connected to a chassis 20 through a solder 20. Namely, in the conventional grounding instructions, the earthing of the first and second printed circuit boards 1 and 2 is performed in a manner that the grounding conduction patterns 12 and 13 oppositely provided on the outer surfaces of the first and second printed circuit boards 1 and are electrically connected by the pin A which is inserted in the through holes formed in the patterns 12 and 13, respectively. Thus, the number of parts required for the grounding construction increases due to the requirement of the pin A. Further, since the grounding conduction patterns 12 and 13 are required to be provided on the outer surfaces of the first and second printed circuit boards 1 and 2 in an opposite relation, a degree of freedom in designing other circuit patterns (not shown) is limited. Further, it is impossible to electrically shield the first printed circuit board 1 from the second printed circuit board 2 due to the provision of the pin A, and the grounding characteristics of the grounding construction is deteriorated due to the provision of the elongated grounding conduction pattern 13 with a narrow width for electrically connecting the pin to the chassis 20.